Health workers wash their hands after taking a blood sample from a child to test for the Ebola virus. On Tuesday, the workers tested people in the village outside Monrovia where a 17-year-old boy died of the disease over the weekend. Abbas Dulleh /AP hide caption

itoggle caption Abbas Dulleh /AP

At the health clinic in Minjibir, Nigeria, a child is immunized for polio. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

The outbreak of Middle East respiratory syndrome is slowing down in South Korea, but people were still wearing surgical masks around Seoul on Monday. Ed Jones/AFP/Getty Images hide caption

itoggle caption Ed Jones/AFP/Getty Images

Airport guards go on patrol wearing masks at Gimpo International Airport in Seoul on Friday. South Korea has announced one more death, but no new cases of the Middle East Respiratory Syndrome coronavirus. Kyodo/Landov hide caption

itoggle caption Kyodo/Landov

A police officer guards the home of a family under a 21-day Ebola quarantine in Freetown, Sierra Leone, back in March. Michael Duff/AP hide caption

itoggle caption Michael Duff/AP